Aristo B64 cold light

[ntenny]

Hi,

In my ongoing enlarger conversion project, I’ve acquired an old Aristo cold light head (old enough to have only one power cord) with a bulb labelled “Aristo Grid Lite B64”. The light looks very blue, and I expect I’ll need a yellow filter to use it with VC paper.

I couldn’t find any information about this bulb, though. I’ve written to Light Sources asking if they have anything; is anyone familiar with the B64 bulb type?

Thanks
-NT

 

[George Collier]

I've used Aristo heads since early 80's and don't remember that name/number. Is it the bulb itself or the fixture?

 

[ntenny]

I've used Aristo heads since early 80's and don't remember that name/number. Is it the bulb itself or the fixture?

It’s the bulb. I’ve been unable to find information on this bulb type, except for one post on LFPF where someone said they had old Aristo literature that mentioned it as a replacement bulb type.

The fixture has no identifying information at all, but it’s a ringer for the one in a 1949 Aristo ad that ran in Popular Photography. I think it’s ancient and possibly intended to fit on a Beseler 5x7.

-NT

 

[ntenny]

Seems no one knows about this bulb. I found a phone app that measures colour temperature and tint; I don’t know how accurate it is, but it showed sane-seeming results in sunlight and for my incandescent enlarger bulb, so I’m guessing it’s basically functional.

The B64 bulb, unfiltered, is too blue to measure: The app says >16000 K and at least +0.03 tint. When I added CC30Y+CC15Y filters, it came down to about 11000 K and just below +0.03 tint. So it looks like filtering this lamp for VC papers will be a significant challenge. I may have to use it only with graded papers, and work towards a controllable LED light source as a more general solution.

-NT

 

[john_s]

Even the (presumably later) Aristo/ZoneVI tubes for the single tube heads were rather blue. I have read contradicting reports of filtering them for VC use. At least one person wrote that a yellow filter in permanent place allowed standard VC filters to be used, others have said that so much filtering is needed that it isn't successfull.

 

[Doremus Scudder]

Your color-temperature meter won't give an accurate reading on a discontinuous light source like a fluorescent tube, especially one that is optimized for blue and green wavelengths only. Color temperature in K is predicated on a black-body spectrum that (usually) contains all wavelengths, just in different proportions. The missing red in the Aristo tube will skew the results to a higher K number.

I would take a look at the light source through a #58 green filter and a #47 blue filter and see what it looked like. These are the color-separation filters for in-camera separation for making color prints from B&W negatives and are rather sharp-cut.

The luminance visible through the #58 filter would be the green component and the low-contrast light for VC paper. Compare this visually and with a light meter to the light transmitted by the #47 filter. All you really need is enough green light to expose through the #00 filter. Even if the blue and green components are not equal, as long as you have enough green to do the job, you'll be able to get a full range of contrasts from VC paper. The only thing is that the increments between filters will not be equally-spaced if the two color components are not balanced. That just means longer exposure times for low-contrast settings and the use of filters closer to the low-contrast extreme if the green component is significantly less than the blue. E.g., to get "normal" contrast, you may have to use a #1.5 or #1 filter instead of #2. If you have a color head, just dial in what you need.

If the light from the cold-light head appears cyan (blue-green) and not just blue, I would wager that it would work just fine with VC papers.

Best,

Doremus

 

[ntenny]

Thanks for the comprehensive reply. I don’t have a blue filter, unfortunately, but I guess I see where the blue/green balance is the important thing and I don’t necessarily need to match the colour of the incandescent bulb. The tint axis is very far towards green, so maybe there’s hope in that respect.

-NT

 

[Doremus Scudder]

Yeah, if you have enough green and blue to get both highest and lowest contrast, then you're in business. It just won't be as evenly spaced as an incandescent.

D

 

[mgb74]

Even the (presumably later) Aristo/ZoneVI tubes for the single tube heads were rather blue. I have read contradicting reports of filtering them for VC use. At least one person wrote that a yellow filter in permanent place allowed standard VC filters to be used, others have said that so much filtering is needed that it isn't successfull.

I did this a while back and it was successful, though I did not feel the contrast changes from 1 though 5 were linear (just by eyeballing). You can find details on the web; I'm not sure I can find my notes. But, as I recall, I used a Roscoe gel that was close to the proper filter but not exact.

 

[MarkS]

A CP40Y or CC40Y is the filter said to correct the "blue" Aristo/Zone VI light source to use modern VC papers. I've been printing with one of those heads for over 30 years. Long ago I tried the yellow filter... didn't make all that much difference. I gave it up and just use under-the-lens VC filters now. This means that I'm often using lower contrast filters than some people would call 'normal'... but there have been very few if any negatives that I could not print. It's true that grade spacing is sometimes non-linear, but I deal with those issues as I go.
It would make sense to have a proper color head or VC head, but so far there have always been more important things to spend money on, and I get good results easily from this non-optimum setup. So it goes.